School closures reduced social mixing of children during COVID-19 with implications for transmission risk and school reopening policies

Abstract

School closures may reduce the size of social networks among children, potentially limiting infectious disease transmission. To estimate the impact of K–12 closures and reopening policies on children's social interactions and COVID-19 incidence in California's Bay Area, we collected data on children's social contacts and assessed implications for transmission using an individual-based model. Elementary and Hispanic children had more contacts during closures than high school and non-Hispanic children, respectively. We estimated that spring 2020 closures of elementary schools averted 2167 cases in the Bay Area (95% CI: −985, 5572), fewer than middle (5884; 95% CI: 1478, 11.550), high school (8650; 95% CI: 3054, 15 940) and workplace (15 813; 95% CI: 9963, 22 617) closures. Under assumptions of moderate community transmission, we estimated that reopening for a four-month semester without any precautions will increase symptomatic illness among high school teachers (an additional 40.7% expected to experience symptomatic infection, 95% CI: 1.9, 61.1), middle school teachers (37.2%, 95% CI: 4.6, 58.1) and elementary school teachers (4.1%, 95% CI: −1.7, 12.0). However, we found that reopening policies for elementary schools that combine universal masking with classroom cohorts could result in few within-school transmissions, while high schools may require masking plus a staggered hybrid schedule. Stronger community interventions (e.g. remote work, social distancing) decreased the risk of within-school transmission across all measures studied, with the influence of community transmission minimized as the effectiveness of the within-school measures increased.

Epidemiology of SARS-CoV-2 infection among staff and students in a cohort of English primary and secondary schools during 2020–2021

“…Modeling studies have suggested the potential importance of school-based transmission of SARS-CoV-2. 36 , 37 However, both the World Health Organization and the European Centres for Disease Control synthesized the evidence during 2021 and concluded that, where mitigations are in place, there is limited evidence for rapid transmission of SARS-COV-2 in schools. 38 , 39 Studies in Germany, 40 Norway, 41 Australia, 42 the UK, 43 , 44 and the USA 45 , 46 have all concluded that, with mitigations in place, the overall risk of transmission in schools was limited.…”

Longitudinal social contacts among school-aged children during the COVID-19 pandemic: the Bay Area Contacts among Kids (BACK) study

“…The effects of stay-at-home orders and physical distancing restrictions may differ between communities. For example, while there is some evidence that school closures are associated with reductions in COVID-19 cases at the state level [ 8 ], the relative effectiveness of closures at averting contact across demographic groups is unknown [ 9 , 10 ]. For example, in a sample from the United States, people in neighborhoods within the lowest income quintile reduced days at work by 6.6% following a stay-at-home order, while those in the highest income quintile reduced days at work by 13.7% [ 10 ].…”

Vaccinations or Non-Pharmaceutical Interventions: Safe Reopening of Schools in England

“…Similar results were found by Panovska-Griffiths et al, who used the Covasim individual-based model 32 , and found that a second wave would likely be induced if schools were reopened in the UK alongside various other restriction relaxations 19 . The potential for negative consequences from school reopening have also been supported by similar studies conducted in other countries and settings 30,33,34 , as well as more abstract work assessing generic school settings under assumed mixing patterns 35 . Many of these works also explore possible mitigation measures such as partial school reopening, reducing classes size and increased testing, with most finding that opening earlier years is less dangerous than later years due to their reduced susceptibilities and fewer contacts.…”